Hi there... I'm new but:
As a person who has dated one half of a couple (and later got involved with the other), I wouldn't get involved in a DADT situation again. My married man didn't tell his wife about me for some 3 years I think... the last 2 years of our relationship she knew some things and the last year itself the 3 of us were more involved together.
From what I know, it want so much that he lied to her for 3 years or actively kept me a secret... she didn't want to know who, just that he'd be out for the night with another. She didn't realize that I was the only other for 3 years running and that we were developing something more than polyfuckery.
Learned my lesson... no more of that ever. When she did find out, she wasn't too happy at first.... but then I wondered if she didn't want to find out things like this well after the fact, then why not inquire during. And then there was the entire walking on eggshelks bit about what she could know.